Herpesviruses: latency and reactivation - viral strategies and host response

Mucosal immunology of the ocular surface

The eye is a sensory organ exposed to the environment and protected by a mucosal tissue barrier. While it shares a number of features with other mucosal tissues, the ocular mucosal system, composed of the conjunctiva, Meibomian glands, and lacrimal glands, is specialized to address the unique needs of (a) lubrication and (b) host defense of the ocular surface. Not surprisingly, most challenges, physical and immunological, to the homeostasis of the eye fall into those two categories. Dry eye, a dysfunction of the lacrimal glands and/or Meibomian glands, which can both cause, or arise from, sensory defects, including those caused by corneal herpes virus infection, serve as examples of these perturbations and will be discussed ahead. To preserve vision, dense neuronal and immune networks sense various stimuli and orchestrate responses, which must be tightly controlled to provide protection, while simultaneously minimizing collateral damage. All this happens against the backdrop of, and can be modified by, the microorganisms that colonize the ocular mucosa long term, or that are simply transient passengers introduced from the environment. This review will attempt to synthesize the existing knowledge and develop trends in the study of the unique mucosal and immune elements of the ocular surface.

The Contribution of Human Herpes Viruses to γδ T Cell Mobilisation in Co-Infections

γδ T cells are activated in viral, bacterial and parasitic infections. Among viruses that promote γδ T cell mobilisation in humans, herpes viruses (HHVs) occupy a particular place since they infect the majority of the human population and persist indefinitely in the organism in a latent state. Thus, other infections should, in most instances, be considered co-infections, and the reactivation of HHV is a serious confounding factor in attributing γδ T cell alterations to a particular pathogen in human diseases. We review here the literature data on γδ T cell mobilisation in HHV infections and co-infections, and discuss the possible contribution of HHVs to γδ alterations observed in various infectious settings. As multiple infections seemingly mobilise overlapping γδ subsets, we also address the concept of possible cross-protection.

Hookworm Infections and Sociodemographic Factors Associated With Female Reproductive Tract Infections in Rural Areas of the Central Region of Togo

Female reproductive tract infections (FRTIs) have a huge impact on women’s health including their reproductive health in rural areas. Immunomodulation by helminth infections could influence the occurrence of FRTIs. This study aimed to investigate the association between FRTIs, hookworm infections, and sociodemographic factors in six rural areas of the central region of Togo. A semi-structured questionnaire was used to collect sociodemographical information, and parasitological assessments were used to diagnose helminth infections. Moreover, cytobacteriological examination of vaginal swabs was performed for the diagnosis of candidiasis and bacterial vaginosis (BV), and real-time PCR method was used to determine sexually transmitted infections (STIs). Finally, a logistic regression analysis was performed to assess the relationship and association of these factors to FRTIs. The prevalence of FRTIs was 82.3% including STIs (74.38%), BV (31.79%), and vulvovaginal candidiasis (9.85%). In detail, FRTIs were caused by bacteria such as Ureaplasma parvum (50%), Ureaplasma urealyticum (26.5%), and Mycoplasma hominis (17.5%) and viruses such us cytomegalovirus (5%) and human papilloma virus (HPV) (20%). No cases of Haemophilus ducreyi, Treponema pallidum, or varicella-zoster virus (VZV) were observed. Interestingly, women who had hookworm infections were at high risk of HPV. The use of condoms was a protective factor [adjusted odds ratio (aOR) = 0.23; 95% CI [0.11–0.51)], while the use of contraceptive methods was a risk factor [aOR = 2.49; 95% CI (1.19–5.19)] for STIs. The risk of BV was lower among participants who had more than four pregnancies [aOR = 0.27; 95% CI (0.11–0.65)]. Furthermore, women who had ever been paid for sexual intercourse were at high probability risk of vulvovaginal candidiasis [aOR = 16.92; 95% CI (1.46–196.48)]. This study highlighted risk factors associated with FRTIs, the control of which would help to reduce the incidence of these diseases. Health-care professionals could develop education and sensitization strategies based on these risk factors, and anti-hookworm treatment concepts may be taken into consideration to minimize the risk of HPV infections.

Herpes DNAemia and TTV Viraemia in Intensive Care Unit Critically Ill Patients: A Single-Centre Prospective Longitudinal Study

Introduction

We analysed blood DNAemia of TTV and four herpesviruses (CMV, EBV, HHV6, and HSV-1) in the REAnimation Low Immune Status Marker (REALISM) cohort of critically ill patients who had presented with either sepsis, burns, severe trauma, or major surgery. The aim was to identify common features related to virus and injury-associated pathologies and specific features linking one or several viruses to a particular pathological context.

Methods

Overall and individual viral DNAemia were measured over a month using quantitative PCR assays from the 377 patients in the REALISM cohort. These patients were characterised by clinical outcomes [severity scores, mortality, Intensive Care Unit (ICU)-acquired infection (IAI)] and 48 parameters defining their host response after injury (cell populations, immune functional assays, and biomarkers). Association between viraemic event and clinical outcomes or immune markers was assessed using χ²-test or exact Fisher’s test for qualitative variables and Wilcoxon test for continuous variables.

Results

The cumulative incidence of viral DNAemia increased from below 4% at ICU admission to 35% for each herpesvirus during the first month. EBV, HSV1, HHV6, and CMV were detected in 18%, 12%, 10%, and 9% of patients, respectively. The incidence of high TTV viraemia (>10,000 copies/ml) increased from 11% to 15% during the same period. Herpesvirus viraemia was associated with severity at admission; CMV and HHV6 viraemia correlated with mortality during the first week and over the month. The presence of individual herpesvirus during the first month was significantly associated (p < 0.001) with the occurrence of IAI, whilst herpesvirus DNAemia coupled with high TTV viraemia during the very first week was associated with IAI. Herpesvirus viraemia was associated with a lasting exacerbated host immune response, with concurrent profound immune suppression and hyper inflammation, and delayed return to immune homeostasis. The percentage of patients presenting with herpesvirus DNAemia was significantly higher in sepsis than in all other groups. Primary infection in the hospital and high IL10 levels might favour EBV and CMV reactivation.

Conclusion

In this cohort of ICU patients, phenotypic differences were observed between TTV and herpesviruses DNAemia. The higher prevalence of herpesvirus DNAemia in sepsis hints at further studies that may enable a better in vivo understanding of host determinants of herpesvirus viral reactivation. Furthermore, our data suggest that EBV and TTV may be useful as additional markers to predict clinical deterioration in ICU patients.

The gammaherpesvirus 68 viral cyclin facilitates expression of LANA

Gammaherpesviruses establish life-long infections within their host and have been shown to be the causative agents of devastating malignancies. Chronic infection within the host is mediated through cycles of transcriptionally quiescent stages of latency with periods of reactivation into detectable lytic and productive infection. The mechanisms that regulate reactivation from latency remain poorly understood. Previously, we defined a critical role for the viral cyclin in promoting reactivation from latency. Disruption of the viral cyclin had no impact on the frequency of cells containing viral genome during latency, yet it remains unclear whether the viral cyclin influences latently infected cells in a qualitative manner. To define the impact of the viral cyclin on properties of latent infection, we utilized a viral cyclin deficient variant expressing a LANA-beta-lactamase fusion protein (LANA::βla), to enumerate both the cellular distribution and frequency of LANA gene expression. Disruption of the viral cyclin did not affect the cellular distribution of latently infected cells, but did result in a significant decrease in the frequency of cells that expressed LANA::βla across multiple tissues and in both immunocompetent and immunodeficient hosts. Strikingly, whereas the cyclin-deficient virus had a reactivation defect in bulk culture, sort purified cyclin-deficient LANA::βla expressing cells were fully capable of reactivation. These data emphasize that the γHV68 latent reservoir is comprised of at least two distinct stages of infection characterized by differential LANA expression, and that a primary function of the viral cyclin is to promote LANA expression during latency, a state associated with ex vivo reactivation competence.

Gammaherpesviruses are ubiquitous viruses with oncogenic potential that establish latency for the life of the host. These viruses can emerge from latency through reactivation, a process that is controlled by the immune system. Control of viral latency and reactivation is thought to be critical to prevent γHV-associated disease. This study focuses on a virally-encoded cyclin that is required for reactivation from latency. By characterizing how the viral cyclin influences latent infection in pure cell populations, we find that the viral cyclin has a vital role in promoting viral gene expression during latency. This work provides new insight into the function of a virally encoded cyclin in promoting reactivation from latency.

Histopathology of brain functional areas in pigs infected by porcine pseudorabies virus

Porcine pseudorabies virus (PRV) infection is a major disease in swine. It is challenging to eradicate the virus entirely after it has invaded Chinese farms, resulting in significant economic losses. This study aimed to explore the histopathological correlation of brain regions in PRV-infected pigs. Twenty pigs were randomly divided into two experimental groups (the PRV-infected and sham-inoculated groups; n = 10 per group). The pigs were then observed for clinical signs at specified time points. Brain tissue samples were collected for histopathological examination on days 3, 10, and 14. The correlation analysis was based on clinical observation, lesion characterization, and pathogen location. Clinical observation showed that the severity of clinical neurological signs increased with time. Pathological dissection and microscopic observation revealed gross pathological changes such as degeneration and necrosis of nerve cells, increase in microglia, eosinophilic inclusion body, lymphocyte infiltration, and loose cortical tissue structure. Immunohistochemistry showed that the virus was mainly localized in neurons, microglia, nerve fibers, cerebellar granular layer, and Purkinje cell layer. The virus invasion route was from the cerebrum to the cerebellum and eventually to the brainstem, and the severity of brain damage increased with time. The route of virus infection was from the olfactory bulb to the hippocampus and eventually to the medulla oblongata, and the viral expression increased with time. Of note, brain injury, viral expression, and clinical neurological signs were positively correlated with the infection period; similarly, the severity and degrees of their changes were positively correlated.

COVID-19 and Herpes Simplex Virus Infection: A Cross-Sectional Study

Background

Despite being variable and poorly characterized, the reported cutaneous manifestations of coronavirus disease 2019 (COVID-19) are of increasing concern.

Methodology

This study aimed to determine the prevalence and possible association between COVID-19 and herpes simplex virus (HSV) infection. A nine-item questionnaire was sent to 120 polymerase chain reaction-confirmed COVID-19 patients with a response rate of 66.67%. This cross-sectional observational study included 80 patients with mild-to-moderate COVID-19 infection who did not require hospitalization or steroid therapy.

Results

One or more HSV infections were observed in 28 patients (35%) with COVID-19 infection, including 10 (35.7%) males and 18 (64.29%) females. Of the 28 patients, fever was reported in 17 (75%) during COVID-19. Most of the respondents (78%) described a single HSV reactivation, 14.29% had two attacks, and 7.14% experienced three attacks. Compared to previous non-COVID-19-related HSV reactivation, the COVID-19-related attacks were more severe in 12 (42.85%) patients, equally severe in five (17.85%) patients, and less severe in one (3.57%) patient. Interestingly, 10 (35.71%) patients developed an initial symptomatic HSV attack during COVID-19 infection.

Conclusions

This study demonstrated a possible association between COVID-19 infection and primary HSV infection or reactivation. COVID-19 direct neuronal effect in addition to COVID-19-related psychological stress, fever, and immunological dysregulation could play a potential role in HSV reactivation or primary infection during COVID-19.

The human oral virome: Shedding light on the dark matter

Mediators of the initiation, development, and recurrence of periodontitis include the oral microbiome embedded in subgingival plaque and the host immune response to a dysbiosis within this dynamic and complex microbial community. Although mediators have been studied extensively, researchers in the field have been unable to fully ascribe certain clinical presentations of periodontitis to their nature. Emergence of high-throughput sequencing technologies has resulted in better characterization of the microbial oral dysbiosis that extends beyond the extensively studied putative bacterial periodontopathogens to a shift in the oral virome composition during disease conditions. Although the biological dark matter inserted by retroviruses was once believed to be nonfunctional, research has revealed that it encodes historical viral-eukaryotic interactions and influences host development. The objective of this review is to evaluate the proposed association of herpesviruses to the etiology and pathogenesis of periodontal disease and survey the highly abundant prokaryotic viruses to delineate their potential roles in biofilm dynamics, as well as their interactions with putative bacterial periodontopathogens and eukaryotic cells. The findings suggest that potential novel periodontal therapies targeting or utilizing the oral virome can alleviate certain clinical presentations of periodontitis. Perhaps it is time to embrace the viral dark matter within the periodontal environment to fully comprehend the pathogenesis and systemic implications of periodontitis.

Recent advancements in our understanding of equid gammaherpesvirus infections

Equid gammaherpesviruses are ubiquitous and widespread in the equine population. Despite their frequent detection, their contribution to immune system modulation and the pathogenesis of several diseases remains unclear. Genetic variability and the combination of equid gammaherpesvirus strains a horse is infected with might be clinically significant. Initial gammaherpesvirus infection occurs in foals peripartum with latency then established in peripheral blood mononuclear cells. A novel EHV-5 study suggests that following inhalation equid gammaherpesviruses might obtain direct access to T and B lymphocytes via the tonsillar crypts to establish latency. EHV-5 is associated with equine multinodular pulmonary fibrosis, however, unlike with EHV-2 there is currently minimal evidence for its role in milder cases of respiratory disease and poor performance. Transmission is presumed to be via the upper respiratory tract with periodic reactivation of the latent virus in adult horses. Stress of transport has been identified as a risk factor for reactivation and shedding of equine gammaherpesviruses. There is currently a lack of evidence for the effectiveness of antiviral drugs in the treatment of equine gammaherpesvirus infections.

TLR3 controls constitutive IFN-β antiviral immunity in human fibroblasts and cortical neurons

Human herpes simplex virus 1 (HSV-1) encephalitis can be caused by inborn errors of the TLR3 pathway, resulting in impairment of CNS cell-intrinsic antiviral immunity. Deficiencies of the TLR3 pathway impair cell-intrinsic immunity to vesicular stomatitis virus (VSV) and HSV-1 in fibroblasts, and to HSV-1 in cortical but not trigeminal neurons. The underlying molecular mechanism is thought to involve impaired IFN-α/β induction by the TLR3 recognition of dsRNA viral intermediates or by-products. However, we show here that human TLR3 controls constitutive levels of IFNB mRNA and secreted bioactive IFN-β protein, and thereby also controls constitutive mRNA levels for IFN-stimulated genes (ISGs) in fibroblasts. Tlr3-/- mouse embryonic fibroblasts also have lower basal ISG levels. Moreover, human TLR3 controls basal levels of IFN-β secretion and ISG mRNA in induced pluripotent stem cell-derived cortical neurons. Consistently, TLR3-deficient human fibroblasts and cortical neurons are vulnerable not only to both VSV and HSV-1, but also to several other families of viruses. The mechanism by which TLR3 restricts viral growth in human fibroblasts and cortical neurons in vitro and, by inference, by which the human CNS prevents infection by HSV-1 in vivo, is therefore based on the control of early viral infection by basal IFN-β immunity.

Herpes Infections in Suspected Cases of Yellow Fever in the Democratic Republic of the Congo

In the battle to quickly identify potential yellow fever arbovirus outbreaks in the Democratic Republic of the Congo, active syndromic surveillance of acute febrile jaundice patients across the country is a powerful tool. However, patients who test negative for yellow fever virus infection are too often left without a diagnosis. By retroactively screening samples for other potential viral infections, we can both try to find sources of patient disease and gain information on how commonly they may occur and co-occur. Several human arboviruses have previously been identified, but there remain many other viral families that could be responsible for acute febrile jaundice. Here, we assessed the prevalence of human herpes viruses (HHVs) in these acute febrile jaundice disease samples. Total viral DNA was extracted from serum of 451 patients with acute febrile jaundice. We used real-time quantitative PCR to test all specimens for cytomegalovirus (CMV), herpes simplex virus (HSV), human herpes virus type 6 (HHV-6) and varicella-zoster virus (VZV). We found 21.3% had active HHV replication (13.1%, 2.4%, 6.2% and 2.4% were positive for CMV, HSV, HHV-6 and VZV, respectively), and that nearly half (45.8%) of these infections were characterized by co-infection either among HHVs or between HHVs and other viral infection, sometimes associated with acute febrile jaundice previously identified. Our results show that the role of HHV primary infection or reactivation in contributing to acute febrile jaundice disease identified through the yellow fever surveillance program should be routinely considered in diagnosing these patients.

Current vaccine approaches and emerging strategies against herpes simplex virus (HSV)

Introduction: Vaccine development for the disease caused by the herpes simplex virus (HSV) has been challenging over the years and is always in dire need of novel approaches for prevention and cure. To date, the HSV disease remains incurable and challenging to prevent. The disease is extremely widespread due to its high infection rate, resulting in millions of infection cases worldwide.Areas covered: This review first explains the diverse forms of HSV-related disease presentations and reports past vaccine history for the disease. Next, this review examines current and novel HSV vaccine approaches being studied and tested for efficacy and safety as well as vaccines in clinical trial phases I to III. Modern approaches to vaccine design using bioinformatics are described. Finally, we discuss measures to enhance new vaccine development pipelines for HSV.Expert opinion: Modernized approaches using in silico analysis and bioinformatics are emerging methods that exhibit potential for producing vaccines with enhanced targets and formulations. Although not yet fully established for HSV disease, we describe current studies using these approaches for HSV vaccine design to shed light on these methods. In addition, we provide up-to-date requirements of immunogenicity, adjuvant selection, and routes of administration.

Simple and rapid high-throughput assay to identify HSV-1 ICP0 transactivation inhibitors

Herpes simplex virus 1 (HSV-1) is a ubiquitous virus that results in lifelong infections due to its ability to cycle between lytic replication and latency. As an obligate intracellular pathogen, HSV-1 exploits host cellular factors to replicate and aid in its life cycle. HSV-1 expresses infected cell protein 0 (ICP0), an immediate-early regulator, to stimulate the transcription of all classes of viral genes via its E3 ubiquitin ligase activity. Here we report an automated, inexpensive, and rapid high-throughput approach to examine the effects of small molecule compounds on ICP0 transactivator function in cells. Two HSV-1 reporter viruses, KOS6β (wt) and dlx3.1-6β (ICP0-null mutant), were used to monitor ICP0 transactivation activity through the HSV-1 ICP6 promoter:lacz expression cassette. A ≥10-fold difference in β-galactosidase activity was observed in cells infected with KOS6β compared to dlx3.1-6β, demonstrating that ICP0 potently transactivates the ICP6 promoter. We established the robustness and reproducibility with a Z'-factor score of ≥0.69, an important criterium for high-throughput analyses. Approximately 19,000 structurally diverse compounds were screened and 76 potential inhibitors of the HSV-1 transactivator ICP0 were identified. We expect this assay will aid in the discovery of novel inhibitors and tools against HSV-1 ICP0. Using well-annotated compounds could identify potential novel factors and pathways that interact with ICP0 to promote HSV-1 gene expression.

Hyaluronic Acid Is an Effective Dermal Filler for Lip Augmentation: A Meta-Analysis

Introduction: The lips and the mouth play an indispensable role in vocalization, mastication and face aesthetics. Various noxious factors may alter and destruct the original structure, and appearance of the lips and the anatomical area surrounding the mouth. The application of hyaluronic acid (HA) may serve as a safe method for lip regeneration. Although a number of studies exist for HA effectiveness and safety, its beneficial effect is not well-established. Aim: The present meta-analysis and systematic review was performed to investigate the effectiveness of HA on lip augmentation. We also investigated the types and nature of adverse effects (AEs) of HA application. Methods: We reported our meta-analysis in accordance with the PRISMA Statement. PROSPERO protocol registration: CRD42018102899. We performed the systematic literature search in CENTRAL, Embase, and MEDLINE. Randomized controlled trials, cohort studies, case series and case reports were included. The untransformed proportion (random-effects, DerSimonian-Laird method) of responder rate to HA injection was calculated. For treatment related AEs descriptive statistics were used. Results: The systematic literature search yielded 32 eligible records for descriptive statistics and 10 records for quantitative synthesis. The results indicated that the overall estimate of responders (percentage of subjects with increased lip fullness by one point or higher) was 91% (ES = 0.91, 95% CI:0.85-0.96) 2 months after injection. The rate of responders was 74% (ES = 0.74, 95% CI:0.66-0.82) and 46% (ES = 0.46, 95% CI:0.28-0.65) after 6 and 12 months, respectively. We included 1,496 participants for estimating the event rates of AEs. The most frequent treatment-related AEs were tenderness (88.8%), injection site swelling (74.3%) and bruising (39.5%). Rare AEs included foreign body granulomas (0.6%), herpes labialis (0.6%) and angioedema (0.3%). Conclusion: Our meta-analysis revealed that lip augmentation with injectable HA is an efficient method for increasing lip fullness for at least up to 6 months after augmentation. Moreover, we found that most AEs of HA treatment were mild or moderate, but a small number of serious adverse effects were also found. In conclusion, further well-designed RCTs are still needed to make the presently available evidence stronger.

Toxoplasma gondii, Herpesviridae and long-term risk of transition to first-episode psychosis in an ultra high-risk sample

BACKGROUND

Ultra high-risk (UHR) criteria were introduced to identify people at imminent risk of developing psychosis. To improve prognostic accuracy, additional clinical and biological risk factors have been researched. Associations between psychotic disorders and infections with Toxoplasma gondii and Herpesviridae have been found. It is unknown if exposure to those pathogens increases the risk of transition to psychosis in UHR cohorts.

METHODS

We conducted a long-term follow-up of 96 people meeting UHR criteria, previously seen at the Personal Assessment and Crisis Evaluation (PACE) clinic, a specialized service in Melbourne, Australia. Transition to psychosis was assessed using the Comprehensive Assessment of the At-Risk Mental State (CAARMS) and state public mental health records. The relationship between IgG antibodies to Herpesviridae (HSV-1, HSV-2, CMV, EBV, VZV) and Toxoplasma gondii and risk for transition was examined with Cox regression models.

RESULTS

Mean follow-up duration was 6.46 (±3.65) years. Participants who transitioned to psychosis (n = 14) had significantly higher antibody titers for Toxoplasma gondii compared to those who did not develop psychosis (p = 0.03). After adjusting for age, gender and year of baseline assessment, seropositivity for Toxoplasma gondii was associated with a 3.6-fold increase in transition hazard in multivariate Cox regression models (HR = 3.6; p = 0.036). No significant association was found between serostatus for Herpesviridae and risk of transition.

CONCLUSIONS

Exposure to Toxoplasma gondii may contribute to the manifestation of positive psychotic symptoms and increase the risk of transitioning to psychosis in UHR individuals.

Epstein-Barr Virus DNA Exacerbates Colitis Symptoms in a Mouse Model of Inflammatory Bowel Disease

Infection with EBV has been associated with various inflammatory disorders including inflammatory bowel diseases (IBD). Contribution of this virus to intestinal disease processes has not been assessed. We previously detected that EBV DNA triggers proinflammatory responses via the activation of endosomal Toll-like receptor (TLR) signaling. Hence, to examine the colitogenic potential of EBV DNA, we used the dextran sodium sulfate (DSS) mouse colitis model. C57BL/6J mice received either DSS-containing or regular drinking water. Mice were then administered EBV DNA by rectal gavage. Administration of EBV DNA to the DSS-fed mice aggravated colonic disease activity as well as increased the damage to the colon histologic architecture. Moreover, we observed enhanced expression of IL-17A, IFNγ and TNFα in colon tissues from the colitis mice (DSS-treated) given the EBV DNA compared to the other groups. This group also had a marked decrease in expression of the CTLA4 immunoregulatory marker. On the other hand, we observed enhanced expression of endosomal TLRs in colon tissues from the EBV DNA-treated colitis mice. These findings indicate that EBV DNA exacerbates proinflammatory responses in colitis. The ubiquity of EBV in the population indicates that possible similar responses may be of pertinence in a relevant proportion of IBD patients.

Viral Respiratory Pathogens and Lung Injury

Several viruses target the human respiratory tract, causing different clinical manifestations spanning from mild upper airway involvement to life-threatening acute respiratory distress syndrome (ARDS). As dramatically evident in the ongoing SARS-CoV-2 pandemic, the clinical picture is not always easily predictable due to the combined effect of direct viral and indirect patient-specific immune-mediated damage. In this review, we discuss the main RNA (orthomyxoviruses, paramyxoviruses, and coronaviruses) and DNA (adenoviruses, herpesviruses, and bocaviruses) viruses with respiratory tropism and their mechanisms of direct and indirect cell damage. We analyze the thin line existing between a protective immune response, capable of limiting viral replication, and an unbalanced, dysregulated immune activation often leading to the most severe complication. Our comprehension of the molecular mechanisms involved is increasing and this should pave the way for the development and clinical use of new tailored immune-based antiviral strategies.

Methods for the Manipulation of Herpesvirus Genome and the Application to Marek's Disease Virus Research

Herpesviruses are a group of double-strand DNA viruses that infect a wide range of hosts, including humans and animals. In the past decades, numerous methods have been developed to manipulate herpesviruses genomes, from the introduction of random mutations to specific genome editing. The development of genome manipulation methods has largely advanced the study of viral genes function, contributing not only to the understanding of herpesvirus biology and pathogenesis, but also the generation of novel vaccines and therapies to control and treat diseases. In this review, we summarize the major methods of herpesvirus genome manipulation with emphasis in their application to Marek’s disease virus research.

Association of Inherited Chromosomally Integrated Human Herpesvirus 6 with Neurologic Symptoms and Management after Allogeneic Hematopoietic Cell Transplantation

Reactivation of human herpesvirus 6 (HHV-6) after allogeneic hematopoietic cell transplantation (HCT) is associated with neurologic complications, but the impact of donor and/or recipient inherited chromosomally integrated HHV-6 (iciHHV-6) on post-HCT central nervous system (CNS) symptoms and diagnostic and therapeutic interventions is not well understood. The aims of the present study were (1) to compare the cumulative incidence of CNS symptoms in the first 100 days following allogeneic HCT among patients with donor and/or recipient iciHHV-6 (iciHHV-6^pos)with that of patients with neither donor nor recipient iciHHV-6 (iciHHV-6^neg) and (2) to assess the role of HHV-6 detection in driving potentially unnecessary interventions in iciHHV-6^pos patients. We performed a retrospective matched cohort study of 87 iciHHV-6^pos and 174 iciHHV-6^neg allogeneic HCT recipients. HHV-6 testing was performed at the discretion of healthcare providers, who were unaware of iciHHV-6 status. The cumulative incidence of CNS symptoms was similar in iciHHV-6^pos (n = 37; 43%) and iciHHV-6^neg HCT recipients (n = 81; 47%; P = .63). HHV-6 plasma testing was performed in similar proportions of iciHHV-6^pos (n = 6; 7%) and iciHHV-6^neg (9%) patients and was detected in all tested iciHHV-6^pos HCTs and 2 (13%) iciHHV-6^neg HCTs. This resulted in more frequent HHV-6-targeted antiviral therapy after iciHHV-6^pos HCT (odds ratio, 12.8; 95% confidence interval, 1.5 to 108.2) with associated side effects. HHV-6 plasma detection in 2 iciHHV-6^pos patients without active CNS symptoms prompted unnecessary lumbar punctures. The cumulative incidence of CNS symptoms was similar after allogeneic HCT involving recipients or donors with and without iciHHV-6. Misattribution of HHV-6 detection as infection after iciHHV-6^pos HCT may lead to unnecessary interventions. Testing for iciHHV-6 may improve patient management.

Multifaceted Roles of ICP22/ORF63 Proteins in the Life Cycle of Human Herpesviruses

Herpesviruses are extremely successful parasites that have evolved over millions of years to develop a variety of mechanisms to coexist with their hosts and to maintain host-to-host transmission and lifelong infection by regulating their life cycles. The life cycle of herpesviruses consists of two phases: lytic infection and latent infection. During lytic infection, active replication and the production of numerous progeny virions occur. Subsequent suppression of the host immune response leads to a lifetime latent infection of the host. During latent infection, the viral genome remains in an inactive state in the host cell to avoid host immune surveillance, but the virus can be reactivated and reenter the lytic cycle. The balance between these two phases of the herpesvirus life cycle is controlled by broad interactions among numerous viral and cellular factors. ICP22/ORF63 proteins are among these factors and are involved in transcription, nuclear budding, latency establishment, and reactivation. In this review, we summarized the various roles and complex mechanisms by which ICP22/ORF63 proteins regulate the life cycle of human herpesviruses and the complex relationships among host and viral factors. Elucidating the role and mechanism of ICP22/ORF63 in virus-host interactions will deepen our understanding of the viral life cycle. In addition, it will also help us to understand the pathogenesis of herpesvirus infections and provide new strategies for combating these infections.

Herpes Simplex Virus 1 Infection of Neuronal and Non-Neuronal Cells Elicits Specific Innate Immune Responses and Immune Evasion Mechanisms

Alphaherpesviruses (α-HV) are a large family of double-stranded DNA viruses which cause many human and animal diseases. There are three human α-HVs: Herpes Simplex Viruses (HSV-1 and HSV-2) and Varicella Zoster Virus (VZV). All α-HV have evolved multiple strategies to suppress or exploit host cell innate immune signaling pathways to aid in their infections. All α-HVs initially infect epithelial cells (primary site of infection), and later spread to infect innervating sensory neurons. As with all herpesviruses, α-HVs have both a lytic (productive) and latent (dormant) stage of infection. During the lytic stage, the virus rapidly replicates in epithelial cells before it is cleared by the immune system. In contrast, latent infection in host neurons is a life-long infection. Upon infection of mucosal epithelial cells, herpesviruses immediately employ a variety of cellular mechanisms to evade host detection during active replication. Next, infectious viral progeny bud from infected cells and fuse to neuronal axonal terminals. Here, the nucleocapsid is transported via sensory neuron axons to the ganglion cell body, where latency is established until viral reactivation. This review will primarily focus on how HSV-1 induces various innate immune responses, including host cell recognition of viral constituents by pattern-recognition receptors (PRRs), induction of IFN-mediated immune responses involving toll-like receptor (TLR) signaling pathways, and cyclic GMP-AMP synthase stimulator of interferon genes (cGAS-STING). This review focuses on these pathways along with other mechanisms including autophagy and the complement system. We will summarize and discuss recent evidence which has revealed how HSV-1 is able to manipulate and evade host antiviral innate immune responses both in neuronal (sensory neurons of the trigeminal ganglia) and non-neuronal (epithelial) cells. Understanding the innate immune response mechanisms triggered by HSV-1 infection, and the mechanisms of innate immune evasion, will impact the development of future therapeutic treatments.

Halting the Spread of Herpes Simplex Virus-1: The Discovery of an Effective Dual αvβ6/αvβ8 Integrin Ligand

Over recent years, αvβ6 and αvβ8 Arg-Gly-Asp (RGD) integrins have risen to prominence as interchangeable co-receptors for the cellular entry of herpes simplex virus-1 (HSV-1). In fact, the employment of subtype-specific integrin-neutralizing antibodies or gene-silencing siRNAs has emerged as a valuable strategy for impairing HSV infectivity. Here, we shift the focus to a more affordable pharmaceutical approach based on small RGD-containing cyclic pentapeptides. Starting from our recently developed αvβ6-preferential peptide [RGD-Chg-E]-CONH2 (1), a small library of N-methylated derivatives (2-6) was indeed synthesized in the attempt to increase its affinity toward αvβ8. Among the novel compounds, [RGD-Chg-(NMe)E]-CONH2 (6) turned out to be a potent αvβ6/αvβ8 binder and a promising inhibitor of HSV entry through an integrin-dependent mechanism. Furthermore, the renewed selectivity profile of 6 was fully rationalized by a NMR/molecular modeling combined approach, providing novel valuable hints for the design of RGD integrin ligands with the desired specificity profile.

Role of CMV chemokine receptor M33 in airway graft rejection in a mouse transplant model

BACKGROUND

Cytomegalovirus (CMV) infection is a risk factor for bronchiolitis obliterans (BO), one form of chronic lung allograft dysfunction (CLAD). The viral chemokine receptor M33 is essential for successful spread of murine CMV to host salivary glands. In the present study we investigated the impact of M33 on chronic airway rejection.

METHODS

MHC I-mismatched tracheas of C·B10-H2^b/LilMcdJ mice were transplanted into BALB/c (H2^d) recipients and infected at different dates with wild type (WT) or M33-deleted (delM33) MCMV representing clinical settings of viral recipient (R)-donor (D)-serostatus: (D-/R+) or (D+/R-). Grafts were recovered for gene expression and histological / immunofluorescence analysis, respectively.

RESULTS

Evaluations showed significantly increased signs of chronic rejection in WT-infected mice compared to uninfected allografts seen in lower epithelium/lamina propria-ratio (ELR) (ELR 0.46 ± 0.07 [WT post] vs. ELR 0.66 ± 0.10 [non-inf.]; p < 0.05). The rejection in delM33-infected groups was significantly reduced vs. WT-infected groups (0.67 ± 0.04 [delM33 post]; vs. WT post p < 0.05). Furthermore, decreased rejection was observed in WT pre-infected compared to post-infected groups (0.56 ± 0.08 [WT pre]; vs. WT post p < 0.05). CD8⁺ T cell infiltration was significantly higher in WT-post compared to the delM33 infected or non-infected allografts.

CONCLUSIONS

These data support the role of the CMV in accelerating CLAD. The deletion of chemokine receptor M33 leads to attenuated rejection.

Structural understanding of non-nucleoside inhibition in an elongating herpesvirus polymerase

All herpesviruses encode a conserved DNA polymerase that is required for viral genome replication and serves as an important therapeutic target. Currently available herpesvirus therapies include nucleoside and non-nucleoside inhibitors (NNI) that target the DNA-bound state of herpesvirus polymerase and block replication. Here we report the ternary complex crystal structure of Herpes Simplex Virus 1 DNA polymerase bound to DNA and a 4-oxo-dihydroquinoline NNI, PNU-183792 (PNU), at 3.5 Å resolution. PNU bound at the polymerase active site, displacing the template strand and inducing a conformational shift of the fingers domain into an open state. These results demonstrate that PNU inhibits replication by blocking association of dNTP and stalling the enzyme in a catalytically incompetent conformation, ultimately acting as a nucleotide competing inhibitor (NCI). Sequence conservation of the NCI binding pocket further explains broad-spectrum activity while a direct interaction between PNU and residue V823 rationalizes why mutations at this position result in loss of inhibition.

Chelonid Alphaherpesvirus 5 Prevalence and First Confirmed Case of Sea Turtle Fibropapillomatosis in Grenada, West Indies

Chelonid alphaherpesvirus 5 (ChHV5) is strongly associated with fibropapillomatosis, a neoplastic disease of sea turtles that can result in debilitation and mortality. The objectives of this study were to examine green (Chelonia mydas), hawksbill (Eretmochelys imbricata), and leatherback (Dermochelys coriacea) sea turtles in Grenada, West Indies, for fibropapillomatosis and to utilize ChHV5-specific PCR, degenerate herpesvirus PCR, and serology to non-invasively evaluate the prevalence of ChHV5 infection and exposure. One-hundred and sixty-seven turtles examined from 2017 to 2019 demonstrated no external fibropapilloma-like lesions and no amplification of ChHV5 DNA from whole blood or skin biopsies. An ELISA performed on serum detected ChHV5-specific IgY in 18/52 (34.6%) of green turtles tested. In 2020, an adult, female green turtle presented for necropsy from the inshore waters of Grenada with severe emaciation and cutaneous fibropapillomas. Multiple tumors tested positive for ChHV5 by qPCR, providing the first confirmed case of ChHV5-associated fibropapillomatosis in Grenada. These results indicate that active ChHV5 infection is rare, although viral exposure in green sea turtles is relatively high. The impact of fibropapillomatosis in Grenada is suggested to be low at the present time and further studies comparing host genetics and immunologic factors, as well as examination into extrinsic factors that may influence disease, are warranted.

Patterns of Genital Tract Mustelid Gammaherpesvirus 1 (Musghv-1) Reactivation Are Linked to Stressors in European Badgers (Meles Meles)

Gammaherpesvirus reactivation can promote diseases or impair reproduction. Understanding reactivation patterns and associated risks of different stressors is therefore important. Nevertheless, outside the laboratory or captive environment, studies on the effects of stress on gammaherpesvirus reactivation in wild mammals are lacking. Here we used Mustelid gammaherpesvirus 1 (MusGHV-1) infection in European badgers (Meles meles) as a host-pathogen wildlife model to study the effects of a variety of demographic, physiological and environmental stressors on virus shedding in the genital tract. We collected 251 genital swabs from 150 free-ranging individuals across three seasons and screened them for the presence of MusGHV-1 DNA using PCR targeting the DNA polymerase gene. We explored possible links between MusGHV-1 DNA presence and seven variables reflecting stressors, using logistic regression analysis. The results reveal different sets of risk factors between juveniles and adults, likely reflecting primary infection and reactivation. In adults, virus shedding was more likely in badgers in poorer body condition and younger than 5 years or older than 7; while in juveniles, virus shedding is more likely in females and individuals in better body condition. However, living in social groups with more cubs was a risk factor for all badgers. We discuss possible explanations for these risk factors and their links to stress in badgers.

Crosstalk Between Epithelial Cells, Neurons and Immune Mediators in HSV-1 Skin Infection

Herpes simplex virus type 1 (HSV-1) infection is highly prevalent in humans, with approximately two-thirds of the world population living with this virus. However, only a fraction of those carrying HSV-1, which elicits lifelong infections, are symptomatic. HSV-1 mainly causes lesions in the skin and mucosae but reaches the termini of sensory neurons innervating these tissues and travels in a retrograde manner to the neuron cell body where it establishes persistent infection and remains in a latent state until reactivated by different stimuli. When productive reactivations occur, the virus travels back along axons to the primary infection site, where new rounds of replication are initiated in the skin, in recurrent or secondary infections. During this process, new neuron infections occur. Noteworthy, the mechanisms underlying viral reactivations and the exit of latency are somewhat poorly understood and may be regulated by a crosstalk between the infected neurons and components of the immune system. Here, we review and discuss the immune responses that occur at the skin during primary and recurrent infections by HSV-1, as well as at the interphase of latently-infected neurons. Moreover, we discuss the implications of neuronal signals over the priming and migration of immune cells in the context of HSV-1 infection.

Human Herpesvirus and the Immune Checkpoint PD-1/PD-L1 Pathway: Disorders and Strategies for Survival

The immune system has evolved as a complex and efficient means of coping with extrinsic materials, such as pathogens and toxins, as well as intrinsic abnormalities, such as cancers. Although rapid and timely activation of the immune system is obviously important, regulated downregulation of the system is almost as significant as activation to prevent runaway immunity, such as allergies and hypercytokinemia. Therefore, the immune checkpoint programmed cell death 1 (PD-1)/programmed cell death ligand 1 (PD-L1) pathway is beneficial for the host. On the other hand, pathogens have evolved to evade host immunity by taking advantage of the PD-1/PD-L1 pathway. This review is focused on human herpesviruses, such as herpes simplex virus (HSV), cytomegalovirus (CMV), and Epstein-Barr virus (EBV), which cause various types of disorders, and their relationships with the PD-1/PD-L1 pathway. Understanding such relationships will be useful for developing preventative and therapeutic methods for disorders caused by herpesviruses.

CHARACTERIZING THE EPIDEMIOLOGY OF HISTORIC AND NOVEL PATHOGENS IN BLANDING'S TURTLES (EMYDOIDEA BLANDINGII)

Pathogens such as herpesviruses, Mycoplasma spp., and frog virus 3-like ranavirus have contributed to morbidity and mortality in many species of free-living and zoo-maintained chelonians. However, their prevalence is understudied in Blanding's turtles (Emydoidea blandingii) across North America. To assess the presence of these pathogens, Blanding's turtles were sampled in Lake County, Illinois, in 2017 (N = 213) and 2018 (N = 160). DNA from cloacal-oral swabs was assayed for four ranaviruses, three Mycoplasma spp., two Salmonella spp., Emydoidea herpesvirus 1 (EBHV1), and tortoise intranuclear coccidiosis (TINC) using a multiplex quantitative polymerase chain reaction (qPCR). Pathogens were most frequently detected in adult turtles (n = 25) and rarely in subadults (n = 2) or juveniles (n = 1). EBHV1 was detected in 22 individuals with no clinical signs of illness, most (n = 20) occurring in the month of May (P < 0.0001). EBHV1 cases at one study site significantly clustered within the same 0.64-km area from 17 to 22 May 2017 (P < 0.0001) and 14 to 15 May 2018 (P = 0.0006). Individuals were rarely positive for Salmonella typhimurium (n = 6). A novel Mycoplasma sp. sharing high homology with other emydid Mycoplasma spp. was detected in one turtle with nasal discharge. Neither TINC nor any ranaviruses were detected. Continued monitoring of this population and habitat may facilitate identification of risk factors for pathogen occurrence and clarify the impact of infectious diseases on Blanding's turtle conservation outcomes.

Viral Involvement in Alzheimer's Disease

Alzheimer's disease (AD) is characterized by the presence of β-amyloid plaques (Aβ) and neurofibrillary tangles (NFTs) in the brain. The prevalence of the disease is increasing and is expected to reach 141 million cases by 2050. Despite the risk factors associated with the disease, there is no known causative agent for AD. Clinical trials with many drugs have failed over the years, and no therapeutic has been approved for AD. There is increasing evidence that pathogens are found in the brains of AD patients and controls, such as human herpes simplex virus-1 (HSV-1). Given the lack of a human model, the route for pathogen entry into the brain remains open for scrutiny and may include entry via a disturbed blood-brain barrier or the olfactory nasal route. Many factors can contribute to the pathogenicity of HSV-1, such as the ability of HSV-1 to remain latent, tau protein phosphorylation, increased accumulation of Aβ invivo and in vitro, and repeated cycle of reactivation if immunocompromised. Intriguingly, valacyclovir, a widely used drug for the treatment of HSV-1 and HSV-2 infection, has shown patient improvement in cognition compared to controls in AD clinical studies. We discuss the potential role of HSV-1 in AD pathogenesis and argue for further studies to investigate this relationship.

The Potential Role of Herpes Simplex Virus Type 1 and Neuroinflammation in the Pathogenesis of Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disease affecting ~50 million people worldwide. To date, there is no cure and current therapies have not been effective in delaying disease progression. Therefore, there is an urgent need for better understanding of the pathogenesis of AD and to rethink possible therapies. Herpes simplex virus type 1 (HSV1) has recently received growing attention for its potential role in sporadic AD. The virus is a ubiquitous human pathogen that infects mucosal epithelia and invades the peripheral nervous system (PNS) of its host to establish a reactivable, latent infection. Upon reactivation, HSV1 spreads back to the epithelium and initiates a new infection, causing epithelial lesions. Occasionally, the virus spreads from the PNS to the brain after reactivation. In this review, we discuss current work on the pathogenesis of AD and summarize research results that support a potential role for HSV1 in the infectious hypothesis of AD. We also highlight recent findings on the neuroinflammatory response, which has been proposed to be the main driving force of AD, starting early in the course of the disease. Relevant rodent models to study neuroinflammation in AD and novel therapeutic approaches are also discussed. Throughout this review, we focus on several aspects of HSV1 pathogenesis, including its primary role as an invader of the PNS, that should be considered in the etiology of AD. We also point out some of the contradictory data and remaining knowledge gaps that require further research to finally fully understand the cause of AD in humans.

Targeting Host Cellular Factors as a Strategy of Therapeutic Intervention for Herpesvirus Infections

Herpesviruses utilize various host factors to establish latent infection, survival, and spread disease in the host. These factors include host cellular machinery, host proteins, gene expression, multiple transcription factors, cellular signal pathways, immune cell activation, transcription factors, cytokines, angiogenesis, invasion, and factors promoting metastasis. The knowledge and understanding of host genes, protein products, and biochemical pathways lead to discovering safe and effective antivirals to prevent viral reactivation and spread infection. Here, we focus on the contribution of pro-inflammatory, anti-inflammatory, and resolution lipid metabolites of the arachidonic acid (AA) pathway in the lifecycle of herpesvirus infections. We discuss how various herpesviruses utilize these lipid pathways to their advantage and how we target them to combat herpesvirus infection. We also summarize recent development in anti-herpesvirus therapeutics and new strategies proposed or under clinical trials. These anti-herpesvirus therapeutics include inhibitors blocking viral life cycle events, engineered anticancer agents, epigenome influencing factors, immunomodulators, and therapeutic compounds from natural extracts.

The Pathogenesis and Immune Evasive Mechanisms of Equine Herpesvirus Type 1

Equine herpesvirus type 1 (EHV-1) is an alphaherpesvirus related to pseudorabies virus (PRV) and varicella-zoster virus (VZV). This virus is one of the major pathogens affecting horses worldwide. EHV-1 is responsible for respiratory disorders, abortion, neonatal foal death and equine herpes myeloencephalopathy (EHM). Over the last decade, EHV-1 has received growing attention due to the frequent outbreaks of abortions and/or EHM causing serious economical losses to the horse industry worldwide. To date, there are no effective antiviral drugs and current vaccines do not provide full protection against EHV-1-associated diseases. Therefore, there is an urgent need to gain a better understanding of the pathogenesis of EHV-1 in order to develop effective therapies. The main objective of this review is to provide state-of-the-art information on the pathogenesis of EHV-1. We also highlight recent findings on EHV-1 immune evasive strategies at the level of the upper respiratory tract, blood circulation and endothelium of target organs allowing the virus to disseminate undetected in the host. Finally, we discuss novel approaches for drug development based on our current knowledge of the pathogenesis of EHV-1.

APOBECs and Herpesviruses

The apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like (APOBEC) family of DNA cytosine deaminases provides a broad and overlapping defense against viral infections. Successful viral pathogens, by definition, have evolved strategies to escape restriction by the APOBEC enzymes of their hosts. HIV-1 and related retroviruses are thought to be the predominant natural substrates of APOBEC enzymes due to obligate single-stranded (ss)DNA replication intermediates, abundant evidence for cDNA strand C-to-U editing (genomic strand G-to-A hypermutation), and a potent APOBEC degradation mechanism. In contrast, much lower mutation rates are observed in double-stranded DNA herpesviruses and the evidence for APOBEC mutation has been less compelling. However, recent work has revealed that Epstein-Barr virus (EBV), Kaposi’s sarcoma-associated herpesvirus (KSHV), and herpes simplex virus-1 (HSV-1) are potential substrates for cellular APOBEC enzymes. To prevent APOBEC-mediated restriction these viruses have repurposed their ribonucleotide reductase (RNR) large subunits to directly bind, inhibit, and relocalize at least two distinct APOBEC enzymes—APOBEC3B and APOBEC3A. The importance of this interaction is evidenced by genetic inactivation of the EBV RNR (BORF2), which results in lower viral infectivity and higher levels of C/G-to-T/A hypermutation. This RNR-mediated mechanism therefore likely functions to protect lytic phase viral DNA replication intermediates from APOBEC-catalyzed DNA C-to-U deamination. The RNR-APOBEC interaction defines a new pathogen-host conflict that the virus must win in real-time for transmission and pathogenesis. However, partial losses over evolutionary time may also benefit the virus by providing mutational fuel for adaptation.

CRISPR/Cas9-Constructed Pseudorabies Virus Mutants Reveal the Importance of UL13 in Alphaherpesvirus Escape from Genome Silencing

Latent and recurrent productive infection of long-living cells, such as neurons, enables alphaherpesviruses to persist in their host populations. Still, the viral factors involved in these events remain largely obscure. Using a complementation assay in compartmented primary peripheral nervous system (PNS) neuronal cultures, we previously reported that productive replication of axonally delivered genomes is facilitated by pseudorabies virus (PRV) tegument proteins. Here, we sought to unravel the role of tegument protein UL13 in this escape from silencing. We first constructed four new PRV mutants in the virulent Becker strain using CRISPR/Cas9-mediated gene replacement: (i) PRV Becker defective for UL13 expression (PRV ΔUL13), (ii) PRV where UL13 is fused to eGFP (PRV UL13-eGFP), and two control viruses (iii and iv) PRV where VP16 is fused with mTurquoise at either the N terminus (PRV mTurq-VP16) or the C terminus (PRV VP16-mTurq). Live-cell imaging of PRV capsids showed efficient retrograde transport after axonal infection with PRV UL13-eGFP, although we did not detect dual-color particles. However, immunofluorescence staining of particles in mid-axons indicated that UL13 might be cotransported with PRV capsids in PNS axons. Superinfecting nerve cell bodies with UV-inactivated PRV ΔUL13 failed to efficiently promote escape from genome silencing compared to UV-PRV wild type and UV-PRV UL13-eGFP superinfection. However, UL13 does not act directly in the escape from genome silencing, as adeno-associated virus (AAV)-mediated UL13 expression in neuronal cell bodies was not sufficient to provoke escape from genome silencing. Based on this, we suggest that UL13 may contribute to initiation of productive infection through phosphorylation of other tegument proteins.IMPORTANCE Alphaherpesviruses have mastered various strategies to persist in an immunocompetent host, including the induction of latency and reactivation in peripheral nervous system (PNS) ganglia. We recently discovered that the molecular mechanism underlying escape from latency by the alphaherpesvirus pseudorabies virus (PRV) relies on a structural viral tegument protein. This study aimed at unravelling the role of tegument protein UL13 in PRV escape from latency. First, we confirmed the use of CRISPR/Cas9-mediated gene replacement as a versatile tool to modify the PRV genome. Next, we used our new set of viral mutants and AAV vectors to conclude the indirect role of UL13 in PRV escape from latency in primary neurons, along with its spatial localization during retrograde capsid transport in axons. Based on these findings, we speculate that UL13 phosphorylates one or more tegument proteins, thereby priming these putative proteins to induce escape from genome silencing.

Unlocking the Role of a Genital Herpesvirus, Otarine Herpesvirus 1, in California Sea Lion Cervical Cancer

Urogenital carcinoma in California sea lions (Zalophus californianus) is the most common cancer of marine mammals. Primary tumors occur in the cervix, vagina, penis, or prepuce and aggressively metastasize resulting in death. This cancer has been strongly associated with a sexually transmitted herpesvirus, otarine herpesvirus 1 (OtHV1), but the virus has been detected in genital tracts of sea lions without cancer and a causative link has not been established. To determine if OtHV1 has a role in causing urogenital carcinoma we sequenced the viral genome, quantified viral load from cervical tissue from sea lions with (n = 95) and without (n = 163) urogenital carcinoma, and measured viral mRNA expression using in situ mRNA hybridization (Basescope®) to quantify and identify the location of OtHV1 mRNA expression. Of the 95 sea lions diagnosed with urogenital carcinoma, 100% were qPCR positive for OtHV1, and 36% of the sea lions with a normal cervix were positive for the virus. The non-cancer OtHV1 positive cases had significantly lower viral loads in their cervix compared to the cervices from sea lions with urogenital carcinoma. The OtHV1 genome had several genes similar to the known oncogenes, and RNA in situ hybridization demonstrated high OtHV1 mRNA expression within the carcinoma lesions but not in normal cervical epithelium. The high viral loads, high mRNA expression of OtHV1 in the cervical tumors, and the presence of suspected OtHV1 oncogenes support the hypothesis that OtHV1 plays a significant role in the development of sea lion urogenital carcinoma.

Seroprevalence and characterisation of herpes simplex virus from human immunodeficiency virus in samples collected from two provinces in South Africa: a retrospective study

Background: Herpes simplex virus (HSV) is a widely distributed human pathogen that is known for its ulcerative lesions at the infection site. HSV can cause persistent infection in the host that is often followed by a period of latency within the neurons. Considering the high rate of HIV infection in South Africa, it is important to assess the seroprevalence of HSV with a focus to determine the epidemiological association between HSV-DNA and HIV-1 in the population. Methods: A total of 44 sera samples were screened for HSV and HIV-1 using the highly sensitive enzyme-linked immunosorbent assay (ELISA). The ELISA positive samples were characterized using polymerase chain reaction (PCR) to confirm the positivity of both viruses and to further differentiate HSV into HSV-1 and -2. Thereafter, the samples were analysed for relatedness using phylogenetic analysis. Results: Of the 44 samples, 36 (81.8%) were positive for HIV-1, while 35 (79.5%) were positive for HSV when screened with ELISA kits. The PCR results, with the use of type specific primers, showed that 4/35 (11.4%) samples were specific for HSV-1 while 30/35 (85.7%) were specific for HSV-2. Statistical analysis performed using the chi-squared goodness-of-fit test showed that there is a significant relationship between HSV-2 and HIV-1 transmission. Conclusions: The prevalence of HSV in the population is high with an increased HSV-2 infection in women. Our study shows that some of the HSV-2 isolates are not related to the clinical isolate SD90e from South Africa, suggesting diversity in HSV-2 viral transmission.

Seroprevalence and characterisation of herpes simplex virus from human immunodeficiency virus in samples collected from two provinces in South Africa: a retrospective study

Background: Herpes simplex virus (HSV) is a widely distributed human pathogen that is known for its ulcerative lesions at the infection site. HSV can cause persistent infection in the host that is often followed by a period of latency within the neurons. Considering the high rate of HIV infection in South Africa, it is important to assess the seroprevalence of HSV with a focus to determine the epidemiological association between HSV-DNA and HIV-1 in the population. Methods: A total of 44 sera samples were screened for HSV and HIV-1 using the highly sensitive enzyme-linked immunosorbent assay (ELISA). The ELISA positive samples were characterized using polymerase chain reaction (PCR) to confirm the positivity of both viruses and to further differentiate HSV into HSV-1 and -2. Thereafter, the samples were analysed for relatedness using phylogenetic analysis. Results: Of the 44 samples, 36 (81.8%) were positive for HIV-1, while 35 (79.5%) were positive for HSV when screened with ELISA kits. The PCR results, with the use of type specific primers, showed that 4/35 (11.4%) samples were specific for HSV-1 while 30/35 (85.7%) were specific for HSV-2. Statistical analysis performed using the chi-squared goodness-of-fit test showed that there is a significant relationship between HSV-2 and HIV-1 transmission. Conclusions: There is a significant positive association between HSV-2 and HIV-1 in the study population. Our study shows that some of the HSV-2 isolates are not related to the clinical isolate SD90e from South Africa, suggesting diversity in HSV-2 viral transmission.

Seroprevalence and characterisation of herpes simplex virus from human immunodeficiency virus in samples collected from the North-West and KwaZulu-Natal Provinces: a retrospective study

Background: Herpes simplex viruses (HSVs) are highly pervasive and show a strong synergistic interaction with human immunodeficiency virus (HIV). High prevalence of HSV type 1 (HSV-1) has been reported in Africa with a prevalence rate of 20-80% in women and 10-50% in men. Studies on the prevalence of HSV in South Africa are few considering the rate of HIV infection in the country. Our focus was to determine the molecular prevalence of HSV-DNA in HIV-1 sera. Methods: In total, 44 convenience samples were screened for HSV and HIV-1 using the highly sensitive enzyme-linked immunosorbent assay (ELISA). The ELISA positive samples were characterized using polymerase chain reaction (PCR) to confirm the positivity of both viruses and to further differentiate HSV into HSV-1 and -2. Thereafter, the samples were analysed for relatedness using phylogenetic analysis. Results: Of 44 samples, 36 (81.8%) were positive for HIV-1, while 35 (79.5%) were positive for HSV when screened with ELISA kits. The results of PCR with type specific primers showed that 4/35 (11.4%) samples were specific for HSV-1 while 30/35 (85.7%) were specific for HSV-2. Statistical analysis performed using chi-squared goodness-of-fit test showed that there is a significant relationship between HSV-2 and HIV-1 transmission. Conclusions: High prevalence of HSV-2 recorded in HIV-1 sera corroborate with similar studies conducted within different cohorts in the continent. SPSS Pearson's chi-squared test established that there is a significant relationship between HSV-2 and HIV-1 transmission.

Seroprevalence and characterisation of herpes simplex virus from human immunodeficiency virus in samples collected from two provinces in South Africa: a retrospective study

Background: Herpes simplex virus (HSV) is a widely distributed human pathogen that is known for its ulcerative lesions at the infection site. HSV can cause persistent infection in the host that is often followed by a period of latency within the neurons. Considering the high rate of HIV infection in South Africa, it is important to assess the seroprevalence of HSV with a focus to determine the epidemiological association between HSV-DNA and HIV-1 in the population. Methods: A total of 44 sera samples were screened for HSV and HIV-1 using the highly sensitive enzyme-linked immunosorbent assay (ELISA). The ELISA positive samples were characterized using polymerase chain reaction (PCR) to confirm the positivity of both viruses and to further differentiate HSV into HSV-1 and -2. Thereafter, the samples were analysed for relatedness using phylogenetic analysis. Results: Of the 44 samples, 36 (81.8%) were positive for HIV-1, while 35 (79.5%) were positive for HSV when screened with ELISA kits. The PCR results, with the use of type specific primers, showed that 4/35 (11.4%) samples were specific for HSV-1 while 30/35 (85.7%) were specific for HSV-2. Statistical analysis performed using the chi-squared goodness-of-fit test showed that there is a significant relationship between HSV-2 and HIV-1 transmission. Conclusions:There is a significant relationship between HSV-2 and HIV-1 in the study population. Our study shows that some of the HSV-2 isolates are not related to the clinical isolate SD90e from South Africa, suggesting diversity in HSV-2 viral transmission.

Understanding Conformational Polymorphism in Ganciclovir: A Holistic Approach

We present a holistic crystallographic study of the antiviral ganciclovir, including insights into its solid-state behavior, which could prove useful during drug development, making the process more sustainable. A newly developed methodology was used incorporating a combination of statistical and thermodynamic approaches, which can be applied to various crystalline materials. We demonstrate how the chemical environment and orientation of a functional group can affect its accessibility for participation in hydrogen bonding. The difference in the nature and strength of intermolecular contacts between the two anhydrous forms, exposed through full interaction maps and Hirshfeld surfaces, leads to the manifestation of conformational polymorphism. Variations in the intramolecular geometry and intermolecular interactions of both forms of ganciclovir were identified as possible predictors for their relative thermodynamic stability. It was shown through energy frameworks how the extensive supramolecular network of contacts in form I causes a higher level of compactness and lower enthalpy relative to form II. The likelihood of the material to exhibit polymorphism was assessed through a hydrogen bond propensity model, which predicted a high probability associated with the formation of other relatively stable forms. However, this model failed to classify the stability of form I appropriately, suggesting that it might not have fully captured the collective impacts which govern polymorphic stability.

In silico analysis of antiviral phytochemicals efficacy against Epstein-Barr virus glycoprotein H

Epstein-Barr virus is a tumor-associated, enveloped virus with glycoprotein receptor gHgL on its surface. gH attaches to epithelial or B cells and mediates internalization. Till date, no specific anti-EBV FDA approved drug is available. Targeting gH may aid in designing virus-specific therapeutics and reducing the drug induced complications in host. We investigated the influence of antiviral phytochemicals on gH using computational approaches. Through molecular docking, we performed binding energy analysis of cellocidin, bruceantin, EGCG, formononetin and sesquiterpene lactones with gH DII/DIII interface, crucial for gH functions. Further, to cause any perturbations in the protein function, the molecules must bind stably to gH. Bruceantin and EGCG interacted with high affinities to gH. Simulation of these two molecules revealed stable binding with gH throughout 100 ns moreover, van der Waal interactions stabilized overall binding. Mutation of amino acids like V265, L269, L315, I423, I459, L474 and F475 involved in stable binding to gH was predicted deleterious to protein function. We obtained no difference in RMSD between these two ligands and minor deviations in the RMSF were noticed compared to gH. Conclusively, our study provided insights into the potential of bruceantin and EGCG to target gH. Different amino acids are involved in binding of each ligand to gH, engagement of certain amino acids may affect the virus binding with epithelial or B cells. The interaction of the ligand with gH may trap it in its native conformation or induce structural flexibility thereby inhibiting the interaction with host receptors or other glycoproteins.Communicated by Ramaswamy H. Sarma.

Herpesviruses and the Type III Interferon System

Type III interferons (IFNs) represent the most recently discovered group of IFNs. Together with type I IFNs (e.g. IFN-α/β), type III IFNs (IFN-λ) are produced as part of the innate immune response to virus infection, and elicit an anti-viral state by inducing expression of interferon stimulated genes (ISGs). It was initially thought that type I IFNs and type III IFNs perform largely redundant functions. However, it has become evident that type III IFNs particularly play a major role in antiviral protection of mucosal epithelial barriers, thereby serving an important role in the first-line defense against virus infection and invasion at contact areas with the outside world, versus the generally more broad, potent and systemic antiviral effects of type I IFNs. Herpesviruseses are large DNA viruses, which enter their host via mucosal surfaces and establish lifelong, latent infections. Despite the importance of mucosal epithelial cells in the pathogenesis of herpesviruses, our current knowledge on the interaction of herpesviruses with type III IFN is limited and largely restricted to studies on the alphaherpesvirus herpes simplex virus (HSV). This review summarizes the current understanding about the role of IFN-λ in the immune response against herpesvirus infections.

Targeting Impaired Antimicrobial Immunity in the Brain for the Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is the most common form of dementia and aging is the most common risk factor for developing the disease. The etiology of AD is not known but AD may be considered as a clinical syndrome with multiple causal pathways contributing to it. The amyloid cascade hypothesis, claiming that excess production or reduced clearance of amyloid-beta (Aβ) and its aggregation into amyloid plaques, was accepted for a long time as the main cause of AD. However, many studies showed that Aβ is a frequent consequence of many challenges/pathologic processes occurring in the brain for decades. A key factor, sustained by experimental data, is that low-grade infection leading to production and deposition of Aβ, which has antimicrobial activity, precedes the development of clinically apparent AD. This infection is chronic, low grade, largely clinically silent for decades because of a nearly efficient antimicrobial immune response in the brain. A chronic inflammatory state is induced that results in neurodegeneration. Interventions that appear to prevent, retard or mitigate the development of AD also appear to modify the disease. In this review, we conceptualize further that the changes in the brain antimicrobial immune response during aging and especially in AD sufferers serve as a foundation that could lead to improved treatment strategies for preventing or decreasing the progression of AD in a disease-modifying treatment.

Biological and environmental factors associated with the detection of elephant endotheliotropic herpesvirus in Asian elephants (Elephas maximus) in Thailand

Elephant endotheliotropic herpesvirus (EEHV) infection is one of the most common diseases in young elephants, causing severe fatal hemorrhagic disease. Subclinical infection was previously described; however, information about the factors associated with virus shedding and reactivation were scarce. To identify the biological and environmental factors related with EEHV detection, blood and oral swab samples were collected from nine captive Asian elephants in Thailand for one year and tested for EEHV presence using real-time PCR. Data including hematological values, management, environmental temperature, and serum cortisol levels were also recorded and analyzed. Results showed that the viral detection frequency ranged from 0-25%. The highest detection frequency was found in the two youngest elephants, aged less than 15 years. Three types of viruses, EEHV1, EEHV4, and EEHV5, were found in this study, which also detected mixed infection in five elephants. Additionally, the study found that sample type, changes in hematological values, management and health issues, and serum cortisol levels were not associated with herpesvirus detection in the elephants. However, EEHV detection percentage was significantly increased in the summer (mid-Feb to mid-May), possibly due to body fitness reduction from food source limitation and low nutrient content. To obtain a broad aspect of EEHV management, long-term EEHV monitoring is highly recommended in every captive elephant herd.

Defects in LC3B2 and ATG4A underlie HSV2 meningitis and reveal a critical role for autophagy in antiviral defense in humans

Recurrent herpesvirus infections can manifest in different forms of disease, including cold sores, genital herpes, and encephalitis. There is an incomplete understanding of the genetic and immunological factors conferring susceptibility to recurrent herpes simplex virus 2 (HSV2) infection in the central nervous system (CNS). Here, we describe two adult patients with recurrent HSV2 lymphocytic Mollaret's meningitis that each carry a rare monoallelic variant in the autophagy proteins ATG4A or LC3B2. HSV2-activated autophagy was abrogated in patient primary fibroblasts, which also exhibited significantly increased viral replication and enhanced cell death. HSV2 antigen was captured in autophagosomes of infected cells, and genetic inhibition of autophagy by disruption of autophagy genes, including ATG4A and LC3B2, led to enhanced viral replication and cell death in primary fibroblasts and a neuroblastoma cell line. Activation of autophagy by HSV2 was sensitive to ultraviolet (UV) irradiation of the virus and inhibited in the presence of acyclovir, but HSV2-induced autophagy was independent of the DNA-activated STING pathway. Reconstitution of wild-type ATG4A and LC3B2 expression using lentiviral gene delivery or electroporation of in vitro transcribed mRNA into patient cells restored virus-induced autophagy and the ability to control HSV2 replication. This study describes a previously unknown link between defective autophagy and an inborn error of immunity that can lead to increased susceptibility to HSV2 infection, suggesting an important role for autophagy in antiviral immunity in the CNS.

Cytomegalovirus chemokine receptor M33 knockout reduces chronic allograft rejection in a murine aortic transplant model

BACKGROUND

Numerous studies suggest that cytomegalovirus (CMV) infection may act as isolated risk factor in the development of cardiac allograft vasculopathy (CAV). Viral G protein-coupled receptors (GPCRs) are thought to contribute to the pathogenic changes associated with CMV infection. The aim of this study was to investigate the role of murine cytomegalovirus GPCR M33 in the development of CAV in a murine aortic allograft model.

METHODS

MHC I-mismatched aortas of C.B10 (H2^b) mice were transplanted into BALB/c (H2^d) recipients, which were either mock-infected, infected with wild type (WT) MCMV or MCMV with a deleted M33-receptor gene (delM33). Persistence of cytomegalovirus infection was confirmed by qPCR and by luciferase assay to ensure active viral replication. Grafts were harvested on days 21 and 37 for intragraft mRNA expression and histological analysis.

RESULTS

Active viral replication was demonstrated and MCMV presence was confirmed by PCR within spleen, liver, salivary glands, lung and the aortic transplant. Infection with delM33 resulted in significantly less intimal proliferation compared to WT-MCMV but more pronounced proliferation than in mock-infected allografts (32.19% [delM33] vs. 41.71% [WT-MCMV] vs. 24.33% [MCMV-]). Intragraft expression of most analyzed genes was significantly increased in infected mice. VCAM-1, ICAM-1, PDGFβ, CXCR3 and Granzyme B were distinctly less expressed in grafts of delM33 infected compared to WT infected mice. Cellular infiltration revealed reduced dendritic cells and T cells in grafts infected with delM33 compared to WT MCMV.

CONCLUSIONS

These data suggest that the MCMV encoded receptor M33 plays an important role as a viral effector mechanism contributing to the development of CAV in a murine aortic transplant model.

Ocular surgery after herpes simplex and herpes zoster keratitis

PURPOSE

The recurrence of herpetic stromal keratitis (HSK) and herpes zoster ophthalmicus (HZO) has been reported after a variety of ocular surgeries. The aim of this study was to review the evidence on the preventive methods employed in the perioperative period in patients having undergone HSK/HZO.

METHODS

The PubMed and Web of Science databases were the main resources used to conduct the medical literature search. An extensive search was performed to identify relevant articles concerning the prophylaxis against and risk of HSK/HZO recurrence in patients undergoing ocular surgery up to December 31, 2019.

RESULTS

The disturbance of the corneal nerve plexus occurs during several ocular surgeries including penetrating keratoplasty, lamellar keratoplasty, corneal cross-linking, cataract surgery, as well as photorefractive and phototherapeutic procedures. Such trauma, as well as modulation of the ocular immunological response caused by steroids applied postoperatively, might engender the HSK/HZO reactivation which is not uncommon. There is strong evidence that oral prophylaxis should be recommended just after surgery in patients undergoing penetrating keratoplasty and having suffered from HSK/HZO. For other types of surgeries, the evidence is less compelling; nevertheless, a period of disease quiescence and oral prophylaxis should still be considered.

CONCLUSIONS

Within the article, we discuss the available evidence for HSK/HZO prophylaxis in ocular surgery. Additional studies would be required to define the real risk of HSK/HZO recurrence following eye surgeries, and particularly cataract surgery, and to confirm the utility of perioperative HSK/HZO prophylaxis.

Epidemiology and biology of a herpesvirus in rabies endemic vampire bat populations

Rabies is a viral zoonosis transmitted by vampire bats across Latin America. Substantial public health and agricultural burdens remain, despite decades of bats culls and livestock vaccinations. Virally vectored vaccines that spread autonomously through bat populations are a theoretically appealing solution to managing rabies in its reservoir host. We investigate the biological and epidemiological suitability of a vampire bat betaherpesvirus (DrBHV) to act as a vaccine vector. In 25 sites across Peru with serological and/or molecular evidence of rabies circulation, DrBHV infects 80-100% of bats, suggesting potential for high population-level vaccine coverage. Phylogenetic analysis reveals host specificity within neotropical bats, limiting risks to non-target species. Finally, deep sequencing illustrates DrBHV super-infections in individual bats, implying that DrBHV-vectored vaccines might invade despite the highly prevalent wild-type virus. These results indicate DrBHV as a promising candidate vector for a transmissible rabies vaccine, and provide a framework to discover and evaluate candidate viral vectors for vaccines against bat-borne zoonoses.

Epstein-Barr virus infection after adolescence and human herpesvirus 6A as risk factors for multiple sclerosis

BACKGROUND AND PURPOSE

Infections with human herpesvirus 6A (HHV-6A) and Epstein-Barr virus (EBV) have been linked to multiple sclerosis (MS) development. For EBV, late infection has been proposed as a risk factor, but serological support is lacking. The objective of this study was to investigate how age affects the EBV and HHV-6A associated risks of developing MS.

METHODS

In this nested case-control study, Swedish biobanks were accessed to find pre-symptomatically collected blood samples from 670 individuals who later developed relapsing MS and 670 matched controls. A bead-based multiplex assay was used to determine serological response against EBV and HHV-6A. Conditional logistic regression was used to calculate odds ratios and 95% confidence intervals.

RESULTS

Seropositivity against EBV exhibited a pattern where associations switched from a decreased risk of developing MS in the group below 20 years of age to an increased risk amongst individuals aged 20-29 and 30-39 years (p for trend 0.020). The age of transition was estimated to be 18.8 years. In contrast, HHV-6A was associated with increased MS risk in all age groups (total cohort odds ratio 2.1, 95% confidence interval 1.6-2.7).

CONCLUSIONS

This study suggests EBV infection after adolescence and age independent HHV-6A infection as risk factors for MS.